Abstract : Factors effecting the performance of a call-back policy are the response biases at successive calls, the available budget and planned sample size, the relative costs of repeated calls, and the desired level of accuracy. By using a mathematical model due to Deming and collecting numerical data on response rates and biases from surveys in practice, this paper presents a systematic evaluation of the effects of these factors and gives advice on the number of calls that should be prescribed for a proposed survey. (Author)